1. Field of the Invention
The present invention relates to a laser scanning device.
2. Description of the Prior Art
In the field of conventional laser scanning devices, for example, JP-A 09-33843 (1997) has proposed a technique in which laser light, emitted by a semiconductor laser, is formed into parallel light rays by using a collimator lens, and these parallel light rays are then deflected by a resonance mirror and converged onto a photosensitive member by a scanning lens having an arcsine characteristic, so that the surface of the photosensitive member is scanned at a constant speed.
Here, the resonance mirror serving as a deflector has a deflection angle range that is smaller than that of a polygon mirror that also serves as a deflector, although it is beneficial in that the size is smaller than that of the polygon mirror. For this reason, in the conventional laser scanning device, the focal distance of the scanning lens needs to be lengthened in comparison with the case where a polygon mirror is used, in order to obtain a desirable scanning width, to cause a longer light path from the resonance mirror to the photosensitive member and the subsequent large size of the device.
Moreover, in order to achieve a laser scanning device with high precision, for example, it is necessary to effectively correct an image-face curvature, on a sub-scanning cross section.